Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 271645
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
945 AM MST TUE JAN 27 2015

.DISCUSSION...STRONG INVERSION REMAINS OVER THE AREA WITH TEMPERATURES
NEAR 50F DEGREES AT 7000FT MSL ON THE BOI SOUNDING. DENSE FOG IS PRESENT
THROUGHOUT THE TREASURE VALLEY...AND THE LOWER ELEVATIONS OF MALHEUR
COUNTY AND HARNEY COUNTY. IMPROVEMENT IN VISIBILITIES IS EXPECTED LATER
THIS AFTERNOON BUT MAY NEED TO EXTEND CURRENT DENSE FOG ADVISORY AN
HOUR OR TWO LATER. WV IMAGERY SHOWS A WEAK UPPER LEVEL LOW MOVING NORTHWARD
OVER SOUTHERN NEVADA. THIS SYSTEM WILL REACH SOUTHERN IDAHO LATER THIS
AFTERNOON. THE BULK OF THIS SYSTEM WILL PASS INTO EASTERN IDAHO WITH
HIGHEST CHANCES OF PRECIPITATION IN THE MAGIC VALLEY...WITH LOWER CHANCES
TO THE NORTH AND WEST. CURRENT FORECAST IS ON TRACK WITH NO UPDATES
EXPECTED.

&&

.AVIATION...IFR/LIFR FOG AND STRATUS COVER MOST OF SE OREGON AND
ALSO MUCH OF THE SNAKE RIVER VALLEY IN SW IDAHO. IMPROVEMENT TO MVFR
AND VFR IS STILL EXPECTED FOR SOME OF THE AREA THIS AFTERNOON...BUT
MID AND HIGH CLOUDS WILL MAKE IT HARDER TO BURN OFF THE LOWER CLOUDS
AND FOG. MAY HAVE TO PUSH BACK THE TIME OF CLEARING IN THE 18Z TAFS.
AN UPPER LEVEL SYSTEM MOVING IN FROM THE SOUTH WILL SPREAD VALLEY
RAIN AND MTN SNOW INTO THE SOUTHERN PORTION OF THE REGION THIS
AFTERNOON AND THEN MAINLY INTO SW IDAHO OVERNIGHT WITH MVFR CIGS.
SFC WINDS GENERALLY SOUTH THROUGH WEST AT 10 KTS OR LESS. UPPER
LEVEL WINDS THROUGH 10K FT SOUTH THROUGH WEST AROUND 10 KTS
TODAY...BECOMING NW 10-20 KTS TONIGHT AND WED.

&&

.AIR STAGNATION...THE STEEP INVERSION IN PLACE THIS MORNING WILL
WEAKEN THIS EVENING AS LIGHT PRECIPITATION MOVES THROUGH THE
AREA. HOWEVER MIXING HEIGHTS THROUGH THE SNAKE RIVER PLAIN WILL
REMAIN BELOW 2000 FEET AGL AT LEAST THROUGH THURSDAY. ANY
RAINFALL WILL INCREASE SURFACE MOISTURE AND THE AID IN THE
REDEVELOPMENT OF FOG OR LOW CLOUDS ACROSS LOWER VALLEYS.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH WEDNESDAY...HIGH CLOUDS HAVE
OVERSPREAD THE REGION AHEAD OF AN UPPER LOW TRACKING NORTH FROM
BAJA. CLOUD COVER HAS DONE LITTLE TO STOP THE DEVELOPMENT OF DENSE
FOG ACROSS SOUTHEAST OREGON AND THE LOWER SNAKE RIVER PLAIN IN
IDAHO. HAVE RAISED A DENSE FOG ADVISORY FOR THESE AREAS THROUGH
LATE MORNING WITH THE POTENTIAL FOR PATCHY BLACK ICE ADDING TO THE
HAZARD. THE UPPER LOW CONTINUES NORTHWARD TODAY...REACHING NE NV
BY LATE AFTERNOON. RAIN AND HIGH ELEVATION SNOW WILL PUSH NORTH OF
THE NV BORDER THIS AFTERNOON WITH SNOW LEVELS BETWEEN 6K-7K FEET.
AS THE LOW TRACKS INTO EASTERN ID TUESDAY NIGHT LIGHT
PRECIPITATION WILL SPREAD FURTHER NORTH AND EAST. BACK EDGE OF
THE PRECIP SHIELD WITH THIS SYSTEM LINES UP FROM ROME OREGON...TO
ONTARIO...TO MCCALL WHICH WILL LEAVE BAKER COUNTY AND MUCH OF
HARNEY COUNTY DRY. PRECIPITATION TAPERS OFF WEDNESDAY MORNING
AND SKIES WILL LIKELY CLEAR ENOUGH OVER SE OREGON AND THE LOWER
TREASURE VALLEY TO ALLOW FOR FOG TO REDEVELOP. TEMPERATURES TODAY
ARE COOLER THAN YESTERDAY BUT WILL REMAIN ABOVE NORMAL THROUGH
WEDNESDAY.

LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY. WEAK RIDGING ON
WEDNESDAY NIGHT WILL GIVE WAY TO THE AREA BEING DOMINATED BY A
SPLIT/NORTHWEST FLOW THROUGH SATURDAY...AS ANOTHER UPPER LOW GETS
CUT OFF IN THE DESERT SOUTHWEST. DRY CONDITIONS ARE EXPECTED DURING
THIS TIME.  BY SUNDAY...BOTH THE GFS AND ECMWF ARE SHOWING THE RIDGE
FLATTENING OUT AND A ZONAL PATTERN SETTING UP. HOWEVER...SHORTWAVES
EMBEDDED IN THAT FLOW ARE LIKELY...BUT THE MODELS ARE VARYING
GREATLY ON TIMING AND PLACEMENT. THE FORECAST IS LARGELY UNCHANGED
FROM THE NEAR CLIMO POPS IN PREVIOUS FORECAST. TEMPERATURES DURING
THIS TIME ARE EXPECTED TO REMAIN NEAR OR ABOVE NORMAL.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING IDZ012-014-033.
OR...DENSE FOG ADVISORY UNTIL 11 AM MST /10 AM PST/ THIS MORNING
     ORZ061-063-064.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...KA
AVIATION.....SP
AIR STAGNATION...DG
PREV SHORT TERM...DG
PREV LONG TERM....EP



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